Short wave radio beacon



Patented; Dec. 5, 1933 SHORT WAVE RAnio BEACON Rene Henri Darbord, Paris, France, assignor to International Communications Laboratories, "1110., New York, N. Y., a corporation of New York L ApplicationJuly 10, 1931. Serial No. 549.924

8 Claims.

' My invention relates to radio beacons for sending out a layer or layers of ultra-short waves for indicating to ships or aircraft the location of the beacon.

The object of my invention is the provision of a specially designed antenna array or assembly producing a rotating field such that the intensity of radiation is the same .in all directions, per-9 pendicular to the axis of the array in a limited layer. The beacon comprises a plurality of n groups of antenna'so arranged that each antenna of one group is spaced from onset the next group, while those of the same group are spaced half a wave length apart. In order to simplify the discussion. the explanation which follows-is confined to two groups of antenna, but it is to be understood that the application may be extended without restriction to n groups.

The antennas are so connected-to. a sourceof oscillating current that the currents in one group ofantennm are equal and inphase. The currents in the other group are also equal andin phase." The currentsin one. group of antennae have the same amplitude as thexcurrents in the other group and are in quadrature with them as tophase. I V

Various features of my invention will be noted from the description to follow. a

My invention is illustrated in the accompanying drawing which showsthe essential features:

Fig. 1 shows an arrayof antennae.

Fig. 2 showsthe plan'of antenna radiation.

Fig. 3 is a horizontal projection of Fig.1.

Fig. 4 shows the" connectionsto the antennae and the compensation device;

Fig. 1 shows an array or groupingof antenna.

Axes o, r, y, z are rectangular. A transmission line placed along 02 feeds the antennae 1, 2, 3T4, etc. parallel to or, and antenna a, b, c, 2 parallel to 0y. The antenna a: parallel to or are spaced half a wave length. The antennae y parallel to 0y The currents in the anten- (see Fig. 2) the field is proportional to the sin 0, I shall represent it by r i 4 l sin 0 sin wt.

In the same way the array 'of antenna y only transmit in the neighborhoodiof the horizontal plane andjsince theantennaazy are in quadraof a' two-phase system of antennae I have thus developed a' rotating" field. The same result could be obtained in a more general manner with a poly-phasesystem'. f Fig. 3 represents -the"horizontal' projection of the antenna group. The supply line consists of a double transmission line made up of four straight conductors AB, CD; a portion of which isrepresented in the figure."

The conductors-AB feedtheantennae l, 2,- '3, 4, etc. It is seen thatantenna'e'of the-same periodicity (1'. 3', 5-- are placed ina similar manner. With the set-up indicated in the figure, it is seenthat two'antennae of dffer'ent periodicity. although theyare separated by a' piece of line at AB of length equal toan' odd number of half wave lengths, are traversed, bycurrents in the same sense. Thus. the parallel antennae"1 ,"2, 3, 4,.etc. are'separated by half 'a wave-length and are traversed by currents inphase. v

The conductors CD feed the antennae (11,1), 0,

d in an analogous manner; these antennae. are 7 separated by half a wave-length and ersedbycurrents in phase. I i I The two lines AB and CD are joined'to the source of oscillations'in sucha way that'the are trav currents in the antennaeand the antennay shall be of .equal amplitude and in quadrature as to phase. "Fig; 4 representsschematicallya part of the antenna groups. If thejunction'oi lines AB and CD'were made without'certainprecautions, the currents in the antennae a: and in the antennae y would-have suitable phases, but their amplitudes would be quite different. For example, suppose that the junction is made at N, at a distance of half a wave-length from the antenna 1 and at a distance of three-quarters of a I wave length from the antenna a.

Let T be the radiation resistance of each antenna, n be the number of antenna of each series (m or y), and Z is the characteristic 1mpedance of each line (AB or CD). At N the line AB is equivalent to a resistance and the line CD is equivalent to a resistance In order that these resistances shall be equal it is necessary that Z equal In practice would be small, of the order of afew ohms, and

w it would be impossible to make a line with straight conductors having an impedance Z equal to a few ohms. This difference is overcome by means of the arrangement represented by the lower part of Fig. 4. Rectangle NPQcqmprises a portion of the line with concentric conductors whose characteristic impedance'can be easily made equal to ,Under these conditions the impedances looking into these two lines at the junction point Q are equal, that is, each has an impedance equal to Moreover, the lengths NPQ and NQ differ by a multiple .of half a wave length and the feeding of the antenna group is correct. Other equivalent compensation devices could beutil-ized, if

desired. a

The axis of, symmetry of the antennae array so arranged that the antennae of one group are separated by an odd number of quarter wave lengths from the antennae of another group.

2. A radio beacon comprising af plurality of antennae divided into two groups about a central axis, the antennae of each group being in parallel relation" and spaced half a wave lengthapart and so arranged that the antennaeof one group are separated-by a quarter of a Wave length from the antenna of another grioup.

. 3, A radio beaconcomprising a plurality of antennae divided into groups, the. antennae of one group being spaced, a quarter of, ,a wave length apart from those of another group and so arranged that the antennae. of each group are in parallel relation.

4. A radio beacon comprising a plurality of antennae divided into groups, the antennae of one group being spaced a quarter of a wave length apart from those of another group and so arranged that the antennae of each group are in parallel relation, means for applying oscillating current to the antennae so the amplitude of current is the same in each group and the phase in one group in quadrature in respect to the phase in the other group.

5 A radio beacon comprising a plurality of antennae divided into two groups disposed symmetrically about a central axis, the antennae of each group being in parallel relation and spaced an odd number of half wave lengths apart and so arranged that the antennae of one group are separated by an odd number of quarter Wave lengths from the antennae of another group, a source of oscillations for said antennae, leads from said source to each of said groups, and compensating means connected in one set of said leads where T is the radiation resistance of each antenna and n is the number of antennae in each group.

6. A radio beacon comprising a plurality of antennae divided into n groups about a central axis, each antenna of one group being spaced a distance equal to'one-half a wave length from the next antenna of the same group, each antenna of .one group being spaced a distance equal to a wave length divided by two times n from an antenna of the next adjacent group, and so arranged that the antenna: of each group are in parallel relation.

7. Aradio beacon comprising a plurality of antennae dividedinto wagroups about a central axis, each antennaof one group being spaced a distance equal to one-half a wave length from the next antenna of the same group, each antenna of one group being spaced a distance equal to a wave length divided by two times 11 from an antenna of the next adjacent group and displaced in a plane perpendicular to the axis of the array through an angle equal to axis, the spacing in each group being such that 1;, 'oneantenna thereof is spaced a distance equal to an odd multiple of a half Wave length from the next antenna, and each antenna of one group being spaced a distance equal to an odd multiple of a wave length-divided by two times 11 from an i antenna of the next adjacent group and so arranged that the antennae of each group are in parallel relation,,an,d means for applying oscillating current to the antennae of said groups so that the amplitude of current is the same in each group and the phase in one group with respect to the phase in another group is as 1:212.

RENE: H. DARBORD. 

